This invention relates to an outboard motor with a turbo-charger and more particularly to an improved turbo-charging arrangement for internal combustion engines, particularly those of the two cycle type.
Recently, there has been an increased interest in the use turbo-charging so as to increase the power of an internal combustion engine without increasing its size or displacement. Although turbo-charging is a very effective way of increasing engine power, it has the well known disadvantage that power is increased primarily at the higher engine speeds. Such internal combustion engines in most applications are required to operate over a wide variety of engine and load speeds, turbo-charging therefore may not provide the desired power increase throughout the entire engine speed rage.
It is, therefore, a principal object of this invention to provide an improved turbo-charging arrangement that will improve the power output at relatively low engine speeds.
It is another object of this invention to provide an improved turbo-charger arrangement that is effective to increase power at relatively low engine speeds thus rendering it applicable for use with outboard motors.
A very popular form of internal combustion engine is the two cycle type. Such type of engines enjoy wide usage in outboard motors and also in relatively small displacement motorcycles. The two cycle engine has a number of advantages, primarily simplicity. Of course, it has been also proposed to employ turbo-charging for improving the output of two cycle engines. However, with crankcase compression two cycle engines, it has been the practice to employ porting arrangements for multiple cylinders engines wherein the firing impulse of one cylinder is used to generate a positive pressure in the exhaust of another chamber so as to prevent the fresh air fuel mixture charge from being discharged from the exhaust port during the periods of overlap between the exhaust port opening and the scavenge port opening. Because of the use of such exhaust tuning to effect what might be considered as "static supercharging", it has been difficult to employ turbo-charging with two cycle engines without adversely affecting performance, particularly at lower engine speeds.
It is, therefore, a further object of this invention to provide an improved turbo-charging arrangement for two cycle engines.
Although turbo-charging has been employed with two cycle engines, it application to outboard motors has been relatively limited. One reason for this is the extreme compact nature of an outboard motor and the difficulties presented in locating a turbo-charger for such a motor in a convenient and safe location and also in providing the adequate flow of exhaust gases to drive the turbo-charger.
It is, therefore, a still further object of this invention to provide an improved, turbo-charged outboard motor.